Why does a plant need nitrogen?

Nitrogen is extremely important for plant growth and photosynthesis, and is particularly crucial for agricultural crops.

  • Nitrogen is extremely important for plant growth and photosynthesis, and is particularly crucial for agricultural crops.
  • It is an essential building block for proteins and DNA.
  • A deficiency or excess of nitrogen often affects crop quality.

The proportion of nitrogen in a plant

The dry weight of a plant consists of an average 1.5% nitrogen, ranging from 0.5% in woody plants to 5.0% in legumes. Only carbon, oxygen and hydrogen are present in higher concentrations. Unlike nitrogen, a plant can capture these nutrients from air and water, meaning they play a modest role in fertilization and soil management.

Promoting growth and photosynthesis

During the vegetative phase (growth phase), nitrogen is the plant’s main control mechanism. It helps plants grow and photosynthesise:

Nitrogen stimulates the process of cell division and cell elongation and extends the growth period.
  • In cell division, the plant grows by adding more cells.
  • In cell elongation, existing cells absorb more moisture, making the plant bigger.

It helps plants grow to sufficient height
and build until it’s time to transition to the generative phase (flowering phase).


By growing bigger, plants have more biomass and surface area to create energy through photosynthesis, ultimately resulting in a higher yield potential.

Plants also need nitrogen to produce chlorophyll.

  • Chlorophyll gives the plant its green colour and is the basis of photosynthesis.
  • In this process, plants – when exposed to sunlight – convert carbon dioxide (CO2) and water (H2O) into glucose (C6H12O6) and oxygen (O2).
General structure of amino acids with the element nitrogen (N)

Building block for proteins and DNA

Nitrogen (N) is an essential element in amino acids and nucleic acids.

  • Amino acids are the building blocks of proteins, which fulfil a variety of biological functions in the plant. Proteins are among the fundamental molecules for living things.
  • Nucleic acids contain a plant’s hereditary information. The best known is deoxyribonucleic acid, better known as DNA.

How do I recognise nitrogen deficiency and nitrogen excess?

Plants absorb nitrogen only in the form of nitrate (NO3-) or ammonium (NH4+). A fertilizer such as calcium ammonium nitrate (CAN) contains these two forms of nitrogen (50/50).

Yellow leaves are an indicator of nitrogen deficiency

Nitrogen-deficient crops can usually be easily distinguished from well-fertilized plants:

  • The plant will develop slower and will have a shorter growth period with early flowering.
  • Nitrogen is mobile in the plant, so its deficiency is first visible through yellowing of the oldest leaves, where a chlorophyll deficit causes the leaf to yellow from tip to centre.

A shortage of nitrogen results in yield loss. But an excess can also have a negative impact:

  • A high nitrogen supply causes large cells holding lots of protein but with thin cell walls.
  • The leaves become too large, dark green and limp, making them susceptible to disease.
  • An abundance of leaves creates a more humid microclimate in the crop, which can encourage fungal development.
  • The plant also stays green and productive much longer when nitrogen is in excess. This is problematic when you want to harvest a finished product.
  • Lush leaf growth can come at the expense of yield in an underground crop.

The right amount of nitrogen is therefore essential for ensuring optimal crop growth.

Explore our nitrogen portfolio

Our nitrogen portfolio includes ammonia, urea, urea ammonium nitrate, calcium ammonium nitrate, diesel exhaust fluid, and other nitrogen products.

Explore products

Mahler, R. (2004). Nutrients Plants Require for Growth. University of Idaho.
Curtis, N. Plant nutrition and soils. Victoria University.
The Mosaic Company (2013). Nitrogen in Plants.
Broekhuizen, J. (2013). Bodem, bemesting en teeltplan.

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